Aion Electronics Lab Series L5 Build

[yuka42]

Should I be seeing DC after C38?  What would the purpose of the diodes be after C38?  D1 and D2.

[EBK]

Should I be seeing DC after C38?  What would the purpose of the diodes be after C38?  D1 and D2.

I suspect those diodes are there to protect pin 3 of IC12, but they are drawn in an odd place on the schematic....

[EBK]

What level of DC are we talking about?
Are you seeing the same level before C38?
I believe you should see no DC.  Everything appears to be ground referenced with no other DC source in sight, unless you have D1 or D2 backwards.

[PRR]

A loudspeaker cable will fit the Output jack. 30V of speaker AC _IN_to the output will blow things up.

The 2K and diodes to rails limit the damage.

C38 may leak a small current. With COMP switch OFF, there is no in-box bleeder path, so there may be some DC voltage. Switching Comp to ON will bleed this. Hanging say 100K at the D1 D2 junction to ground will bleed this.

[yuka42]

okay.  Thanks again for the lessons.  It was in the millivolts after C38 which eventually, on second inspection, drained to naught.  Just kinda grasping at straws is all.  I've since found that the garble did not go away but in my fiddling, the comp section was shorted to ground.  Fixed the bridge and now back to square one.  I have reheated as much of the comp section solder points as I can and examined this thing with a fine tooth comb for solder bridges etc.  My only other remaining thought is perhaps something is bridging in the IC sockets themselves which seems unlikely and a massive pain to remove.  I have discovered (perhaps) some more clues but have been researching things to try to wrap my brain around the circuit a bit.  Reading on the CA3080 and it's operation etc (which is, I'll admit, a bit above my pay grade).

Here's a fantastic write up...for someone smarter than I.
http://www.diystompboxes.com/smfforum/index.php?topic=63724.0

-I've socketed all 3 transistors and when Q2 (2N3906) is removed, the audio clears up and sounds great (and obviously the comp section stops working). 
-with Q2 removed, the audio is clear all the way up to the cathodes of D4 and D5.  On the anodes it sounds crackly, which worsens when the comp level is adjusted to the louder.
-I'm using Tayda's version of the 1N914 for those...which look different than Aion's and digi2t's. 

-with Q2 and Q3 Installed and the 3080 removed i see -7.14V on the socket pin 5. 

-seeing how pin 5 on the CA3080 is the bias input....does it make sense that I would see -12.28V on that pin with both Q2 and Q3 removed and the IC is installed?  I would assume it would be 0V since it's an input.  (I'm thinking very linear-ly.)  Or have I blown pin 5?

The way I'm envisioning (read guessing) this thing working, is that when the comp is OFF, the CA3080 works as a normal opamp with a FET after it's output.  When the comp is ON, the audio goes through IC12 and is rectified and amplified through the diodes and Q2, then transmitted to the bias input on pin 5 of the 3080.  Thereby forcing it to react to the bias and change it's output level (e.g. compress)?   I'm not exactly understanding the purpose of the darlington, other than as a part of the LED circuit.  I'm probably way out to lunch, but I do love a good sandwich. 

[yuka42]

http://www.diystompboxes.com/smfforum/index.php?topic=113344.msg1049106#msg1049106

Essentially the same circuit in the design stage with Aion.  I learned a bit from it though so thanks PRR!   

[bsas]

Hi all!

I just started this build and I am on the "parts hunt phase".
I was wondering if anyone that has the pedal working could measure the amp drainage of it. I am looking for a couple of AC/AC adapters and I am not sure what is the minimum miliamps that it needs to provide.

Thanks!!!

[digi2t]

Hi all!

I just started this build and I am on the "parts hunt phase".
I was wondering if anyone that has the pedal working could measure the amp drainage of it. I am looking for a couple of AC/AC adapters and I am not sure what is the minimum miliamps that it needs to provide.

Thanks!!!

There's a link in the build doc that points towards suitable power supplies. For what they cost, I always go bigger when it comes to power supplies. A 1000mA adapter doesn't cost much more than a 500mA or 750mA. For 2 or 3 dollars more, I say go for it.

[bsas]

The thing is that I found a 400mA adapter that is very small and white.
I like that it is white because then I will not mix with my DC adapter and burn my other pedals. And I like the size because of portability. I just want to know if 400mA is enough, I am not worried about price (specially on this build).

[bsas]

Ah! Also I was suffering to find a 2.5kA pot (i even asked you on youtube ), but I have an idea that I would like to share and ask if it is crazy:

If I get a 5kA dual pot (which is very easy to find on Tayda) and I join each top lead to the bottom one, I think it will behave like a 2.5kA because 2xR  parallel resistors should give me R/2 resistance (so 2x5k = 2.5k), and being log taper (both tracks) I think it should give me a similar taper behavior (that is the part I am not sure).

Am I tripping or does that make sense? Thanks!!!

[EBK]

Ah! Also I was suffering to find a 2.5kA pot (i even asked you on youtube ), but I have an idea that I would like to share and ask if it is crazy:

If I get a 5kA dual pot (which is very easy to find on Tayda) and I join each top lead to the bottom one, I think it will behave like a 2.5kA because 2xR  parallel resistors should give me R/2 resistance (so 2x5k = 2.5k), and being log taper (both tracks) I think it should give me a similar taper behavior (that is the part I am not sure).

Am I tripping or does that make sense? Thanks!!!

I've done that trick before.  It works fine.

[bsas]

Build report: main parts soldered! Please let me know if you guys spot any obvious problems.
Waiting for big parts to arrive, like pots, 3PDT and enclosure.




P.S.: Love when the solder points look like Hershey kisses

[slacker]

-I've socketed all 3 transistors and when Q2 (2N3906) is removed, the audio clears up and sounds great (and obviously the comp section stops working). 
-with Q2 removed, the audio is clear all the way up to the cathodes of D4 and D5.  On the anodes it sounds crackly, which worsens when the comp level is adjusted to the louder.

Sounds like your problem is round this area, you shouldn't really hear any audio on the anodes of d4 and d5, C39 should be smoothing the signal into a DC voltage. If you're getting audio there that would explain why it sounds garbled. I would try replacing C39 and making sure you have continuity between the positive end of C39 and the diodes and from the negative end and -V, also check the value and connections to R94

[yuka42]

Thanks for reply Slacker!!  You inspired me to take another peek at the pedal today. I decided to replace the Tayda 1n914 diodes with a pair I got from mouser which match every other Lab build has that I've seen. And what do ya know......the garble stopped. Comp working as it should. No more DC on the output. LED is lighting as it should. After all that routing around it must've been those diodes. As much of a headache it was to sort that problem out I sure learned a lot about the circuit and the CA3080 in the process. I walk away a smarter man. Haha. And I've got a wicked pedal. So thanks everyone for the inspiration and helping hand.

Kudo's to Kevin at Aion. Must've been some amount of work to put this into pedal form. It sounds great. The sweepable mid frequency is the most useful thing to have in a recording studio pedal board and it sounds fantastic. Very excited to put this thing through its paces.

Ryan

[bsas]

Hi all!

So, my turn of having weird issues with the build

1) Children boards LEDs behavior:

First I tried to wire the LEDs in the standard "on/off" mode where you "link" both small boards by the "CH" lug. The LEDs never turned off. The weird thing is that both 3PDT were working fine and doing what there were suppose to do but the bypass LED and the channels LED were always on.

Then I removed the link and I wired the CH from the channel select board directly to ground (the "always on channel LEDs option) and all LEDs work fine now, with a small exception that the bypass LED is never fully "off". It is like very weak light while off and very strong while on.

2) Compressor muting the note attack instead of compressing:

The pedal sound OK, I guess, and everything looks like it is working but the compressor is very weird. Basically I can see it acting and it's LED blinks when it grabs a high peak note as expected, but sound wise, instead of compressing the signal, it mutes the attack of the note and the volume comes back slowly. It almost sounds like a buggy noise gate.

3) Low output:

Being a preamp pedal I was expecting a monster amplification, but, for me I need to put volume at 12 and master almost at 12 to be kind of unity level. Am I missing something here?

4) A lot of heat from voltage regulators:

The voltage regulators run quite hot all the time. I already measured the +|- 15V pins and they measured perfectly. Is that expected?

Thanks all!!!

[bsas]

Interesting findings:

I can measure voltage on the Q3(MPSA13) pins, but, if I remove it, the sound of the compression stays the same (AKA bad). Seems to me that somehow it is getting ignored. I already tried to replace the MPSA13 with a couple others and it doesn't help.

Also, when I turn the unit ON the compressor LED lights up and fades out slowly...

[jstone]

Hey all,

I just finished this build. Everything works and sounds pretty good, but I'm having difficulty calibrating the distortion trimpot. I have a 1kHz sine wave measuring 30mV with my cheapo Radio Shack DMM:



However, when I apply the signal to pin 2 of IC10 (CA3080), I don't get anywhere near the 4.4V AC required by the spec at pin 6. I'm getting readings in the millivolt range no matter where I set the trimpot.



Am I doing something incorrect or is there a problem with my IC? As you can see from the pic, I'm applying the signal directly to pin 2 and measuring at pin 6 rather than using the test pads (I forgot to solder pins to the test pads and now can't reach them easily).  My black test lead on my DMM is connected to the common ground at the input jack.  I have the pedal powered on with a Line6 Px-2g 9VAC power supply. The V+ and V- on the pedal are right around 15 volts, as they should be, including as measured on pins 4 and 7.

Any help would be most appreciated!

Thanks,

Jason

[digi2t]

Was the headphone volume set all the way up before you dialed in the 30mV?

Maybe the compressor is interfering? Adjust the compressor trimmer and see if it affects the distortion voltage. If so, adjust it to the end, so as it raises the distortion voltage. Then go back to the distortion trimmer. Then set the compressor.

I'm just spitballing here.

[jstone]

Was the headphone volume set all the way up before you dialed in the 30mV?

Maybe the compressor is interfering? Adjust the compressor trimmer and see if it affects the distortion voltage. If so, adjust it to the end, so as it raises the distortion voltage. Then go back to the distortion trimmer. Then set the compressor.

I'm just spitballing here.

Yes, the headphone volume was up all the way. I'll try the compressor trimmer. Thanks.

[bsas]

Turn the compressor switch off, so it will remove it from the circus and will isolate the distortion circuit